If you want to speak loud and clear, use this megaphone app. The microphone of your device becomes the loudspeaker of your phone, but with a limited range. This way, you can still make a speech even when you are far away from the microphone. 

Megaphone - Voice Amplifier is the best app for those who want to talk to their friends without the microphone in their ear. It is also an excellent choice for those who need a way to be heard. The microphone is limited to a maximum volume and a minimum distance.

How to use it:

Start the Megaphone app. Press the middle button to turn your device's mic into a speaker.